I MUST get better mileage, Project Autotragic

[91CavGT]

Hello again everyone. After taking a long break from hypermiling, I am back. But this time, I have different motivation to try to increase FE. Now I MUST get better mileage. Why you may ask? Because I am now driving about 3,000 miles a month for work, and I am NOT getting reimbursed for mileage!!


So a little about my ride. It is a 2001 Mitsubishi Mirage ES sedan. It has a 1.8L SOHC 16 valve motor that is rated at 116 hp and 111 ft lbs, but unfourtunately it is connected to an automatic transmission. I hate autos, but I had to buy one. I have had 2 foot surgeries in the last 2 years to try to help my knees out, so working a clutch pedal has gotten too hard to do, especially with how much I drive now.

EPA lists highway MPG to be 30, city MPG to be at 22, and combined to be at 25. I'm already above these marks due to implementing hypermile techniques. On top of that, I just bought a Scan Gauge II yesterday so things should only improve from here!!

So here is a picture of what the car looked like when I bought it.



It had 104,000 miles on it, had been in the guy's family since 2002, and had been taken care of. He was asking $2k, but due to a noisy wheel bearing (it didn't have any play yet) I talked him down to $1900 and bought it.

After spending a little on replacing the front wheel bearings the gas mileage improved by about 2 mpg and it was ready to be used for travel, a LOT of travel!!

[91CavGT]

So fast forward a couple of weeks and Here is what the car looks like now.



The wheel covers were badly cracked and about to fall off so I just took them off and I had to get the windows tinted. Why did I have to do that? Here's the reason..........




I am traveling all across the South East U.S. installing GPS trackers in fleet vehicles for one company. I sometimes have 100 of these units in my back seat and I needed DARK tint to make sure no one in hotel parking lots can look in to see what I have in the car. To try to help prevent peeping Toms, I also put a blanket over the top of the boxes. I can't move them into the trunk because it is full too, here is how it looks.............




So not only do I need to get an automatic car to get better fuel economy, I am battling a lot of extra weight that must be carried in the car as well.

[91CavGT]

So I have been logging fuel economy pretty close for the last couple of weeks to try to see where the sweet spot is for this car. I made a small chart to keep track of what I have found.........

Speed A/C on or off MPG

70 mph on 30-32 mpg
65 mph on 32-34 mpg

65 mph off 34-36 mpg
60 mph off 36-39 mpg
55 mph off 39-42 mpg


So now I have a pretty good baseline to go by. So now what? Well, my next step was to purchase a Scan Gauge II. I drove to Orlando yesterday and picked it up. On the way back to the hotel, I decided to get some more information as to power requirements at different speeds as well as with the A/C on and off. Now, I realize that the Scan Gauge II is not 100% accurate on it's horsepower readouts. However, I am just using this number as a basis for power needed to maintain a given speed on level ground without drafting. Here is what I found.............



At 55 mph, the car is turning about 2250 rpm and it requires approximately 20.6 hp to maintain that speed. This was with the A/C off.




At 60 mph, the car is now turning about 2500 rpm and requires an additional 2 hp up to 22.6hp to maintain speed. Once again, A/C was off.




Now at 65 mph the car is now turning about 2700 rpm, and required power to maintain speed is now going up at a much faster pace. It is up to 28.3 hp now. A/C off.




Now at 70 mph the motor is buzzing along at 3,000 rpm and now requires a staggering 33.5 hp to maintain speed!! Once again, A/C off.



So how much power does it take to run the A/C while at cruising speed? Well, let's find out............



Still at 70 mph, still turning about 3,000 rpm, but now it takes 38.8 hp to maintain speed! So that is a hair more than 5 hp just to run the A/C. This is why my car was getting so much better gas mileage without the A/C on.


So as we can see, once you cross over the 60 mph mark with my car (1.8L auto sedan as a refresher) then gas mileage really starts to plunge due to the required hp to maintain speed. This tells me that the aerodynamics are not very good and there is room for improvement. Unfourtunately, due to the high rpm that this motor turns on the highway, massive gains MAY be difficult to get with just aero mods. Also, now that I know what rpm the motor is turning, I can see how both the intake AND exhaust is a restriction just at cruising speeds.

[91CavGT]

Where's the facepalm smilie? I put this in the wrong forum!!! I meant to put it in the Projects forum. My bad.

[trollbait]

If you haven't already, pump up the tire pressure to the sidewall max.

60mph as the fuel economy tipping point has been my experience. An air dam will clean up air flow under the car, and is simpler than an underbelly pan. I've repurposed the black plastic garden edging for that in the past.

A manual lock up control for the transmission might help. The ecomodder wiki has an article on how to do it. It's cheap but has a high pita potential depending on access to the transmission wire harness.

[91CavGT]

Originally Posted by trollbait

If you haven't already, pump up the tire pressure to the sidewall max.

60mph as the fuel economy tipping point has been my experience. An air dam will clean up air flow under the car, and is simpler than an underbelly pan. I've repurposed the black plastic garden edging for that in the past.

A manual lock up control for the transmission might help. The ecomodder wiki has an article on how to do it. It's cheap but has a high pita potential depending on access to the transmission wire harness.

Thanks for the info.


I've experimented with different tire pressures and currently am running 36 psi(30 psi on sticker in door jam) . That seems to be a good trade off between uneven tire wear and good fuel economy. Since I am driving 3,000+ miles a month, I don't want to air the tires up too much for fear of wearing the center of the tires out too fast. Once I stop carrying all this weight, I'll air them up to their max rating of 44 psi and carry more speed in the corners, in the name of keeping momentum up of course!

Since I am currently about 1,000 miles away from home, the modifications that I can do out here are minimal, but I think I can do an air dam mod at the hotel. Considering this car currently has no air dam, it may prove to be very effective!

[Jay2TheRescue]

Originally Posted by 91CavGT

Thanks for the info.


I've experimented with different tire pressures and currently am running 36 psi(30 psi on sticker in door jam) .... Once I stop carrying all this weight, I'll air them up to their max rating of 44 psi and carry more speed in the corners, in the name of keeping momentum up of course!

If you're carrying a lot of weight in the car, go ahead and air them up to the max sidewall pressure.

[91CavGT]

Originally Posted by Jay2TheRescue

If you're carrying a lot of weight in the car, go ahead and air them up to the max sidewall pressure.

Sometimes I've got an additional about 400 pounds in the car, other times it's down to only about 150 pounds of extra weight. Even if I drive 3,000+ miles a month do y'all think this wouldn't cause excess wear in the center of the tires?






I just went by Lowes and picked up some garden edging, some L brackets for support, some self tapping screws, bolts, nuts, and washers!! I'm gonna make an air dam first, then with what I have left of the edging, I'm gonna try to make some side skirts.

[Jay2TheRescue]

It should not create excess wear running at the max sidewall pressure. I've been running my vehicles at the max sidewall pressure for over 20 years and I have never encountered center wear on any of my tires. The only one I don't run at the max sidewall is my 98 GMC K1500. I'm running E rated 1 ton tires at 70 PSI (80 Max) The stock tired are basically LT tires with a 35 PSI max sidewall pressure.

[91CavGT]

Originally Posted by Jay2TheRescue

It should not create excess wear running at the max sidewall pressure. I've been running my vehicles at the max sidewall pressure for over 20 years and I have never encountered center wear on any of my tires. The only one I don't run at the max sidewall is my 98 GMC K1500. I'm running E rated 1 ton tires at 70 PSI (80 Max) The stock tired are basically LT tires with a 35 PSI max sidewall pressure.

Thanks for the info!